Disable nullability checks in file shared between the managed type sy…

…stem and ILVerificationTests (dotnet#84382)

This file is shared between the managed type system and the ILVerificationTests suite.
The managed type system doesn't have nullable checks turned on, but ILVerificationTests does. This was causing build failures in PRs that build the ILVerificationTests.

We should enable nullable checking in the future in the managed type system as a whole at some point, but we aren't there yet.

src/coreclr/tools/Common/TypeSystem/Common/Utilities/CustomAttributeTypeNameParser.cs

@@ -7,6 +7,8 @@
 
 using Internal.TypeSystem;
 
+#nullable disable
+
 namespace Internal.TypeSystem
 {
     public static class CustomAttributeTypeNameParser